We recently discovered the pentapeptide mimic 1,4-Bis (9-0 dihydroquinidinyl) phthalazine / hydroquinidine 1,4-phathalazinediyl diether (C-61) as a tyrosine kinase inhibitor targeting the substrate-binding P-site of SYK as a novel drug candidate against B-lineage acute lymphoblastic leukemia (ALL), the most common form of childhood cancer. In the proposed translational multidisciplinary research project, we will prepare rationally- designed C-61 nanoparticle constructs for more effective delivery of C-61 to leukemia cells in an attempt to further improve its potency and broaden its therapeutic window. Throughout the project, the anti-leukemic activity of the generated C-61 nanoparticles will be evaluated using in vitro and in vivo assay platforms, including quantitative in vitro apoptosis assays, murine BCL-I leukemia model in immunocompetent mice, and SCID mouse xenograft models of human B-lineage ALL. Under Specific Aim 1, we will develop potent and stable liposomal 1st generation nanoparticle constructs of C-61 by optimizing the intemal core environment and inner monolayer of the large unilamellar liposomal vesicles for maximized C-61 entrapment. Under Specific Aim 2, we will develop potent 2nd generation liposomal nanoparticle constructs of C-61 with improved pharmacodynamic features by modifying the outer monolayer of the large unilamellar liposomal vesicles with poly(ethylene glycol)-modified lipids. Under Specific Aim 3, we will develop CD19- directed 3rd generation nanoparticle constructs of C-61 by incorporating anti-CD19 scFv covalently attached to PEGylated phospholipids in the outer layer of the lead 2nd generation nanoparticles. Under Specific Aim 4, we will study the anti-leukemic activity of the lead CD19-specific 3rd generation C-61 nanoparticle constructs in side by side comparison to standard chemotherapy drugs. Under Specific Aim 5, we will study the effects of standard anti-leukemia drugs on toxicity, pharmacokinetics, and efficacy of the lead CD19-specific 3rd generation C-61 nanoparticle constructs. The development of cell-type specific nanoparticles targeting SYK-dependent anti-apoptotic survival mechanism in CD19-f- leukemic cells will be a significant step forward to overcome chemotherapy resistance in childhood B-lineage ALL. The successful completion of this research project may provide the foundation for a more effective and potentially paradigm-shifting treatment strategy for B-lineage ALL, the most common form of childhood cancer. New nanotechnology discoveries that will result from our research are anticipated to significantly contribute to the mission of the NCI Alliance for Nanotechnology in Cancer.